using System;

using Org.BouncyCastle.Asn1;
using Org.BouncyCastle.Asn1.Pkcs;

namespace Org.BouncyCastle.Asn1.Smime
{
	public class SmimeCapability
		: Asn1Encodable
	{
		/**
		 * general preferences
		 */
		public static readonly DerObjectIdentifier PreferSignedData = PkcsObjectIdentifiers.PreferSignedData;
		public static readonly DerObjectIdentifier CannotDecryptAny = PkcsObjectIdentifiers.CannotDecryptAny;
		public static readonly DerObjectIdentifier SmimeCapabilitiesVersions = PkcsObjectIdentifiers.SmimeCapabilitiesVersions;

		/**
		 * encryption algorithms preferences
		 */
		public static readonly DerObjectIdentifier DesCbc = new DerObjectIdentifier("1.3.14.3.2.7");
		public static readonly DerObjectIdentifier DesEde3Cbc = PkcsObjectIdentifiers.DesEde3Cbc;
		public static readonly DerObjectIdentifier RC2Cbc = PkcsObjectIdentifiers.RC2Cbc;

		private DerObjectIdentifier capabilityID;
		private Asn1Object			parameters;

		public SmimeCapability(
			Asn1Sequence seq)
		{
			capabilityID = (DerObjectIdentifier) seq[0].ToAsn1Object();

			if (seq.Count > 1)
			{
				parameters = seq[1].ToAsn1Object();
			}
		}

		public SmimeCapability(
			DerObjectIdentifier	capabilityID,
			Asn1Encodable		parameters)
		{
			if (capabilityID == null)
				throw new ArgumentNullException("capabilityID");

			this.capabilityID = capabilityID;

			if (parameters != null)
			{
				this.parameters = parameters.ToAsn1Object();
			}
		}

		public static SmimeCapability GetInstance(
			object obj)
		{
			if (obj == null || obj is SmimeCapability)
			{
				return (SmimeCapability) obj;
			}

			if (obj is Asn1Sequence)
			{
				return new SmimeCapability((Asn1Sequence) obj);
			}

			throw new ArgumentException("Invalid SmimeCapability");
		}

		public DerObjectIdentifier CapabilityID
		{
			get { return capabilityID; }
		}

		public Asn1Object Parameters
		{
			get { return parameters; }
		}

		/**
		 * Produce an object suitable for an Asn1OutputStream.
		 * <pre>
		 * SMIMECapability ::= Sequence {
		 *     capabilityID OBJECT IDENTIFIER,
		 *     parameters ANY DEFINED BY capabilityID OPTIONAL
		 * }
		 * </pre>
		 */
		public override Asn1Object ToAsn1Object()
		{
			Asn1EncodableVector v = new Asn1EncodableVector(capabilityID);

			if (parameters != null)
			{
				v.Add(parameters);
			}

			return new DerSequence(v);
		}
	}
}
